[mythtv-users] "NVP: prebuffering pause" "NVP::AddAudioData():p2: Audio buffer overflow, audio data lost!" "WriteAudio: buffer underrun"

"José Tomás @ Chico" jose.tomas at chico.mine.nu
Tue Oct 14 21:22:13 UTC 2008


Mike, thank you!
The issue is bad signal.

Q:Why does I say this?
A:If I connect directly to first provider cable outlet inside my house, 
works fine, if I connect at my 5th outlet and last in row the issue occurs.
For those who doesn't know the signal between outlets drops the power, 
portion dropping mainly depends in items connected to the outlets.
Provider only give us in a SLA manner an amount of signal. In my case 
the signal has some channel frequencies with low quality, but with SLA 
ok for the first outlet.

Now I believe that my tuner whit a chip saa7134 has his own contribution.
When you have digital, channel usually exists or don't, with non 
digital, my case, we have the gray, not white nor black... blarg...
Probably saa7134 doesn't provides image or audio in a way mythtv can not 
record or shall I say can not synchronize with.

Do you believe that this symptom should be reported on that page?

Mike, once more, thank you.


Michael T. Dean wrote:
> On 10/13/2008 07:53 PM, José Tomás @ Chico wrote:
>> Michael T. Dean wrote:
>>> On 10/13/2008 02:45 PM, José Tomás @ Chico wrote:
>>>> I'm having this issue for some channels of poor signal quality. 
>>>> So lot's of messages in log saying that: "NVP: prebuffering 
>>>> pause" or even sometimes during channel change 
>>>> "NVP::AddAudioData():p2: Audio buffer overflow, audio data lost!"
>>>>  plus "WriteAudio: buffer underrun"
>>>> Regarding what I found googling this is an old issue, but in 
>>>> those posts I didn't found the solution. Post more then 1 year 
>>>> old. It's like mythtv is not synchronizing correctly the signal.
>>>> Do you know anything about?
>>>> My TV singal is standard cable, not digital.
>>> http://www.mythtv.org/wiki/index.php/Prebuffering_pause and, if 
>>> yours isn't there, when you figure it out, please update the page 
>>> with another cause/solution.
>> Good! I didn't found read that page.
>> Nevertheless the issue stands. I made a new DB, so everything fresh 
>> and configured taking care the recommendations. What I did noticed is
>>  if select on of those channels where I get no image, the issue 
>> happens.
>> If I get out of Watch TV and then get back, about 5 sec after getting
>> out, I'm able to see the channel correctly. These channels have the
>> worst quality among the others.
>> What can these show?
> Well, if you have poor signal quality, it may result in corrupt
> recordings (it does for digital capture, but I have no idea how your
> capture card/encoder will handle it for analog signals).  I would assume
> that poor signal on an analog capture card would simply result in
> static/noise which would be encoded into a valid video stream, meaning
> that the recording itself would not be corrupt.
> If your recording is /not/ corrupt, you may just need to enable the setting:
> Extra audio buffering
> Enable this setting if MythTV is playing "crackly" audio and you are
> using hardware encoding. This setting will have no effect on MPEG-4 or
> RTJPEG video. MythTV will keep extra audio data in its internal buffers
> to workaround this bug.
> (which is enabled by default and should never be disabled, so please
> ensure it's enabled on yours).
> If, however, you have corrupt recordings, you may have a problem.
> TTBOMK, there's nothing you can do to "fix" Myth's playback of
> corrupt/broken recordings.  If your signal issues are causing your
> recordings to be corrupt, you really need to fix the signal quality
> issue, which is something I'm trying to do myself, as signal quality for
> nearly all my local over-the-air digital channels has dropped
> significantly--from nearly perfect reception with no bit errors for
> almost 2 years to just usable--within the last 6 months.  I'm just
> hoping I find a better solution than the "ultimate" solution--which is
> to stop using the channel.
> Good luck,
> Mike
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*José Tomás*
 MSN: jfht at netc.pt
 Skype: jfhtomas

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